Epoxy resins have excellent mechanical properties, electrical properties, chemical resistance, etc. and further have excellent adhesion to various materials, and hence, have widely been used as an adhesive or a coating agent. For instance, epoxy resins have excellent adhesion to fiber glass reinforced plastics (abbreviated as "FRP") and are useful as an adhesive for FRP-made parts. However, when these epoxy resin adhesives are used, they must usually be temporarily cured by heating, where the squeezed out adhesive should be cut off by sanding or with knife, and because the cured epoxy resin is too hard and brittle, it is hardly cut off with knife.